A. Field of the Invention
This invention relates generally to monitoring systems, and more particularly to systems for automatically monitoring the programs broadcast by commercial television stations.
B. Description of the Prior Art
Several techniques for monitoring the programs broadcast by commercial television stations are known. The simplest technique involves a human monitor who watches the programs broadcast at a monitoring site and manually logs each program. Automated systems have been developed which employ a "picket fence" code placed in the upper corners of the picture broadcast by the television station which is automatically detected and recorded. Preferably the code is broadcast in such a manner that it is undetectable by the viewer. In prior art systems, this is accomplished by placing the code in a corner of the television field that is not normally visible to the viewer. In other systems, the code is placed in a notch that has been filtered out of the audio spectrum.
While these techniques provide a way to monitor the television programs broadcast by commercial television stations, registration problems occur when the bar code is recorded on a photographic medium, and when the code is placed in the audio spectrum, the code can be heard during quiet periods. Furthermore, these systems are generally used only to identify commercials, and are not particularly suitable for monitoring the programs carried by network affiliated television stations to determine whether a network program is being carried. This is because of the large amount of data involved in monitoring a network program line-up, and because no convenient data storage format has been developed to store this data. As a result, the effort required to monitor all of the network affiliated stations and to tabulate the data becomes excessive if more than minimal data about the programs broadcast is tabulated.